Oxidation of 8mass percent percent Y_2O_3 centre dot ZrO_2/CoNiCrAlY Thermal Barrier Coating by Heating at High Temperature and Delamination of Top Coat

摘要

Thermal barrier coating (TBC) was applied on the Co based superalloy specimens, where CoNiCrAlY bond coat was deposited by high velocity oxygen fuel (HVOF) spraying and 8 mass percent percent yttria stabilized zirconia (YSZ) top coat by atmospheric plasma spraying. The isothermal oxidation behavior of TBC at high temperature was characterized by scanning electron microscopy, EPMA mapping analysis, energy dispersive spectroscopy and X-ray diffraction The Alumina and complex oxide layers were formed along the interface between the top coat and the bond coat, and the thickness of the oxide layers increased with increasing heating temperature and holding time. When the delamination of the top coat occurred during the holding of the specimen at 1473K for 1732ks and on cooling after holding at 1273K for 3960ks, half-sphere-shaped cracks grew along the interface between unmelted bond coat particles and Al_2O_3 layer, and propagated in the complex oxide or the top coat In tensile test and edge-indent test, the delamination of top coat started near the top of particles and extended in the top coat under shear stress.